An agricultural vehicle known as a “combine” harvester is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning. A combine includes a header which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves, and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves onto a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. The cleaning system includes a cleaning fan which blows air through oscillating sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material such as straw from the threshing section proceeds through a straw chopper and out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
A “header” can broadly include row crop headers (such as corn headers) and cutting platforms (such as bean headers). In the case of a corn header, the header typically includes a number of row units with each row unit including a feed/snapping unit positioned at the bottom side thereof. Each feed/snapping unit typically includes a pair of stripper plates spaced apart from each other and extending in a direction of the row crop, a pair of stalk rolls positioned underneath the stripper plates, and a pair of gathering chains for moving the stalks into the space between the stripper plates and moving the stripped ears of corn rearwardly. It is also known to provide the header with a number of chopping units, with each chopping unit being associated with a respective row unit. As the corn stalks are stripped downwardly through the stripper plates by the stalk rolls, the chopping units chop the stalks, leaves, etc. (also known as “material other than grain” or MOG) into finer pieces which are then distributed onto the field.
It is known to separate the mechanical input drive at the header between the feed/snapping units and the chopping units. A single mechanical input drive is provided on the header, and the input drive is split in a parallel manner onboard the header between the feed/snapping units and the chopping units. The parallel feed from the single input drive to the feed/snapping units can be configured with a variable operating speed by varying the shaft speed of the input drive, and the other parallel feed to the chopping units can be somewhat constant at a given input drive speed by varying a gear ratio within a transmission. However, as the operating speed of the single input drive changes the operating speed of the chopping units also changes. During this transitional speed change, this can result in an operating speed of the chopping units which is below a desired threshold operating speed as the input drive speed from the base unit changes. Moreover, since the shaft speed of the single input drive can infinitely vary between upper and lower operating ranges, but the transmission only has discrete stepped gear ratios, the operating speed of the chopping units is not constant.
What is needed in the art is a header for an agricultural harvester which better accommodates different drive needs of various sub-systems onboard the header.